The formation of uniform layers on semiconductor substrates necessitates that the environment inside the deposition chamber of deposition tools, such as chemical vapor deposition (CVD) tools, be continuously monitored and cleaned for residue build-up and contaminants. Consider, for instance, a plasma enhanced chemical vapor deposition (PECVD) tool. Such a tool is commonly employed to deposit material layers, such as silicon dioxide (SiO2) or fluorinated silicate glass (FSG) on a substrate, such as a silicon wafer. It is well known that over a period of use, the material layers form as deposits on the walls of a deposition chamber. The buildup of these material layer deposits is undesirable because the deposits can flake off from the chamber's interior surfaces and introduce defects into the substrate and overlying layers and decrease the uniformity of layers being deposited on the substrate and the overall quality of the device.
To reduce the build-up of material layer deposits, the deposition chamber is periodically cleaned in situ, usually using a fluorine-containing cleaning gas, referred to as a gaseous fluorocompound. Periodic in situ cleaning is typically done in-between chemical deposition procedures being performed on one or more batches of substrates. In situ cleaning procedures attempt to provide a balance between efficient chamber cleaning in a minimum period and using a minimum amount of fluorocompound. For instance, a conventional cleaning procedure uses a two-step process where the cleaning gas is introduced at two different rates: a high flow and a low, for the first and second steps, respectively. Over time, however, such cleaning procedures become less effective, leading to increased numbers of defective semiconductor devices being produced in the chamber. Moreover, as the yield of functional devices produced from the chamber continues to decrease, it eventually becomes necessary to stop semiconductor device fabrication and replace the dome of the deposition chamber, thereby increasing the overall costs of semiconductor device fabrication.
Accordingly, what is needed in the art is an efficient in situ cleaning process that allows the production of semiconductor devices with low numbers of defects and thereby extend the time between dome changes of the deposition chamber.